The present disclosure relates to methods for producing ruthenium nanoparticles characterized by face-centered cubic or hexagonal closed packed crystallographic structure, small particle size, and a narrow distribution of particle size.
Ruthenium catalysts are increasingly becoming of interest for various applications such as the reduction of carbon monoxide in automobile exhaust gas, steam reforming of shale gas, the selective oxidation of fuel streams for polymer electrolytic fuel cells, and for the generation of various chemical products.
Various processes for producing ruthenium nanoparticles are known. However, the ruthenium nanoparticles prepared by such processes are typically deficient in one or more respects including large particle size, non-homogeneous particle size distribution, agglomerated nanoparticles, nanoparticles that are difficult to disperse, nanoparticles having significant surface contamination, populations of nanoparticles having a large percentage of nanoparticles deviating from an isotropic spherical shape, and/or poor high temperature stability. Such defects limit the catalytic utility and/or efficiency of ruthenium catalysts. It is believed that at least some of these inherent deficiencies of some prior art processes result from a protracted and un-controlled ruthenium nucleation phase that “fixes” a non-homogeneous distribution of nuclei from which ruthenium nanoparticles are formed during a deposition (growth) phase.
Accordingly, there is a need in the art for methods for controllably producing ruthenium nanoparticles having a desired crystallographic structure, small particle size, homogeneous particle size distribution, uniform spherical shape, and temperature stability.